The purpose of the proposed research is to elucidate some of the chemical and physical factors involved in growth regulation during organogenesis and, more specifically, to determine the mechanism by which nerve promotes regeneration of embryonic kidney and liver. The possibility that the growth promoting factor provided by nerve is either cyclic AMP or a substance that regulates cyclic nucleotide concentrations in the target cell will be investigated. Macromolecular changes during in vitro organ resynthesis in the presence or absence of nerve and chemical growth factors will be monitored. The possibility that active developmental transitions are determined by changes in intracellular levels of cAMP will be explored. The in vitro aggregation from cells in suspension which i propose to use in this study provides a simplified model system for analyzing cell-to-cell interactions during tissue and organ construction. Any insight into the nature of integrative factors which regulate growth and tissue interactions during development is useful in that it may provide us with the tools necessary both to promote regrowth in organs which normally do not regenerate and also to inhibit the growth of cells whose control mechanisms are abnormal.